The over-arching goal of this proposal is to develop powerful new methods for identifying multiple cortical sources associated with different early visual areas to reveal the cortical loci of abnormality in amblyopia and strabismic suppression. Technologies such as fMRI, EEG and MEG have enabled us to image the human brain during cognition, but have had limited application for the study of cortical dynamics of closely spaced visual areas. Modem fMRI methods can be used to identify some participating cortical loci but can easily overlook others since a disruption of temporal information within an area may not cause an overall change in cortical activation. Moreover, fMRI's limited temporal resolution obscures feedback processes between cortical areas. EEG and MEG have fine temporal resolution but to date have had limited success in identifying individual cortical sources. The project goals are to develop new methods that solve these problems and apply them to understanding the cortical deficit associated with amblyopia and strabismic suppression. Three Specific Aims are proposed: Aim 1: To develop new VEP/MEG methods for separating multiple cortical sources located in striate and extrastriate areas. Classical methods alone are unable to separate closely spaced early and late visual areas. A successful outcome of this aim will enable cortical dynamics of both early and late visual areas to be reliably distinguished. Aim 2: Amblyopia is a developmental disorder of spatial vision, which occurs in about 3% of the population. Many years of research confirm the deficit is cortical in origin with recent findings indicating involvement of visual areas beyond V1. To reveal the spatio-temporal participation of different cortical areas that contribute to amblyopia and strabismic suppression, we will apply the new evoked response (ER) methodology of Aim 1 that solves past limitations in identifying multiple cortical sources. The research will be able to determine not only where amblyopic/strabismic loss has occurred, but also the role of feedback between visual areas. Aim 3: Use fMRI and psychophysics to validate and extend the findings of ER experiments on the cortical site(s) of the deficit in amblyopia. In addition, novel stimuli such as ambiguous figures that are not readily employed using ER methods, will be employed to examine and distinguish areas that participate in the deficit associated with amblyopia. [unreadable] [unreadable]